Which statement most completely describes the role of the cell in a single celled organism

Many life forms consist of a single cell. As well as simple bacteria, there are more complex organisms, known as protoctists. Unlike bacteria, they have complex internal structures, such as nuclei containing organized strands of genetic material called chromosomes. Most are single-celled, but some form colonies, with each cell, usually remaining self-sufficient.

Prokaryotes are unicellular organisms whose cells lack a nucleus. A nucleus is a dense are in a cell that contains nucleic acids the chemical instructions that direct the cell's activities.

Not sure if this really helps but...here you go!

The correct answer is d